The company said current non-executive chairman David Tyler would step down on March 9 and be succeeded by Scicluna, who holds the same role at insurer RSA, the next day.

It said last July that Scicluna would take over from Tyler, who has been chairman for the past nine and a half years, but did not give a precise date.

Scicluna starts the job at a difficult time, after Britain's competition regulator said last month its initial view was that Sainsbury's purchase of Walmart's Asda should be blocked in the absence of the sale of a large number of stores, or even one of the brands.

The regulator will publish a final ruling by April 30. Sainsbury's Chief Executive Mike Coupe, seen as the architect of the deal, could come under investor pressure if it fails.

Industry data published this week also showed Sainsbury's continuing to underperform rivals, including market leader Tesco and No. 4 Morrisons.

At current run rates, Sainsbury's could lose its No.2 status to Asda when the next data set is published on April 30.

(Reporting by James Davey; Editing by Mark Potter)